Electrical, rheological properties and morphologies of biphasic blends filled with carbon nanotubes in one of the two phases

The present study compares two biphasic blends constituted by immiscible thermoplastics: polypropylene (PP)/polycaprolactone (PCL) and polyamide 12 (PA12)/PCL, both filled with carbon nanotubes (CNT). The experimentations, led with the aim to point up the differences between the two blends, were carried out on the rod formed samples (diameter 1.5 mm) just after extrusion or pelletization. During this process, CNT are first introduced in PCL and then mixed with PP or PA12. These two blends can comprise different kinds of morphologies depending on components weight fractions. The electrical conductivity is affected by the blend morphology on one hand and by the localization of CNT on the other hand. Even with a similar mixing sequence, CNT localization is different between the two blends. CNT migration from PCL to PA12 was highlighted in the PA12/PCL blend, in comparison with the PP/PCL blend where CNT stay in PCL.. Different experimental techniques such as selective phase extraction, microscopy analyses (SEM and TEM), rheology measurements and interfacial energy calculations based on surface tension measurements, can explain the different behaviours of each blend. A correlation between the observed morphology and the wetting coefficient calculated with experimental measurements of surface tensions allowed to predict CNT localization.